1. Field of the Invention
The present invention relates to an exhaust gas recirculation device for an internal combustion engine (hereinafter, sometimes referred to as an EGR device), and especially relates to an EGR device in which a filter for trapping particulates in an exhaust gas is arranged in a recirculation gas route (hereinafter, sometimes referred to as an EGR gas route).
2. Related Art Statement
Usually, in order to decrease an amount of NOx in an exhaust gas, use is made of a method of recirculating the exhaust gas in which a part of the exhaust gas is derived from an exhaust system of an internal combustion engine and is returned to an air intake system thereof. In this method, since particulates included in the exhaust gas are also returned to an engine, an abrasion of engine parts such as a value, a piston and so on, due to the returned particulates is very hard, and thus there exists a problem such that a life of the engine as well as an engine performance is decreased extraordinarily.
In order to eliminate the drawback mentioned above, an abrasion performance is made excellent by improving a material of engine parts, or a filter is arranged in a recirculation gas route. Such a technic is known from for example Japanese Patent Laid-Open Publication No. 62-255510 (JP-A-62-255510). However, the material improvement of engine parts can not eliminate the drawback mentioned above fundamentally. Moreover, when use is made of the filter for trapping the particulates, a pressure loss is increased abruptly since a stuffing of the filter is caused by the particulates in the recirculation gas route. Therefore, there occurs a drawback such that an EGR rate defined by a rate of recirculation of the exhaust gas is largely deviated.